Rotary laser level with laser detection

ABSTRACT

A method of detecting a laser beam emitted by a laser tool includes receiving light via an optical window of a receiver unit, and directing the light received via the optical window onto a first light sensor array and a second light sensor array. At least one signal is output from the first light sensor array indicating a characteristic of the light incident upon the first light sensor array. At least one signal is output from the second light sensor array indicating a characteristic of the light incident upon the second light sensor array. The at least one signal from the first light sensor array and the at least one signal from the second light sensor array are processed with respect to each other to produce a measurement signal. A determination is then made whether the received light is a laser beam emitted by the laser tool based on the measurement signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 61/747,254 entitled “Rotary Laser Level” by Munroe et al., filedDec. 29, 2012, U.S. Provisional Application Ser. No. 61/786,269 entitled“Rotary Laser Level” by Munroe et al., filed Mar. 14, 2013, and U.S.Provisional Application Ser. No. 61/786,239 entitled “Rotary LaserLevel” by Munroe et al., filed Mar. 14, 2013, the disclosures of whichare hereby incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates generally to laser levels and inparticular to rotary laser levels.

BACKGROUND

Rotary laser levels are measurement and layout tools that are configuredto project a laser beam in a complete 360° circle. Positioning a rotarylaser level in the center of a room or work area enables a level laserline to be projected around the entire room or work area. This enablesall types of work to be performed including site grading, laying outfoundations for building construction, installing drop-ceilings, pouringconcrete, installing chair rails, installing fences, and more. Rotarylaser levels are either of the manual or automatic leveling type. Manualleveling requires that the operator manually adjust the level of thelaser beam to achieve level positioning. In rotary laser levels withautomatic leveling, the laser assembly is typically mounted on apendulum arrangement and is configured to use gravity and/or a levelingmechanism, such as a servo-motor, to achieve level positioning.

Some rotary laser levels are configured to work with a remote unit. Theremote unit is capable of controlling the operation of the laser levelremotely so that a single person can operate the laser level. The remoteunit may also include a laser detector or receiver. This facilitates thedetection of the laser beam outdoors, and also allows other informationto be determined, such as horizontal and vertical reference positions,and distance measurements.

There are a number of issues that are faced in the using and caring forrotary laser levels. For example, rotary laser levels are valuable toolswhich make them a target for thieves. In addition, they require a highdegree of accuracy which may require regular servicing and calibrationchecks to maintain. Because the remote/receiver unit is a separatedevice from the base unit, care must be taken to ensure that theremote/receiver unit does not become misplaced and that theremote/receiver unit is charged.

DRAWINGS

FIG. 1 depicts a perspective view of a rotary laser level system inaccordance with the present disclosure with the receiver unit of thesystem docked to the base unit.

FIG. 2 depicts a perspective view of the rotary laser level system ofFIG. 1 with the receiver unit being removed from the base unit.

FIG. 3A depicts a perspective view of the base unit of the rotary laserlevel system of FIG. 1 with the receiver unit removed.

FIG. 3B depicts an exploded view of the base unit of FIG. 3A.

FIG. 4 depicts a bottom perspective view of the base unit.

FIG. 5 depicts a perspective view of the base unit mounted on a tripod.

FIG. 6 depicts a block diagram of the components of the base unit.

FIG. 7 depicts a block diagram of the power system of the base unit.

FIG. 8 depicts the base unit during a rotational mode of operation.

FIG. 9 depicts the base unit during a line mode of operation.

FIG. 10 depicts the base unit during a point mode of operation.

FIG. 11A depicts an embodiment of the receiver unit of FIG. 1.

FIG. 11B depicts a first exploded view of the receiver unit of FIG. 11A.

FIG. 11C depicts a second exploded view of the receiver unit of FIG.11A.

FIG. 12 depicts a block diagram of the components of the receiver unit.

FIG. 13 depicts a block diagram of the power system of the receiverunit.

FIG. 14A depicts a block diagram of the theft prevention and detectionsystem of the base unit.

FIG. 14B depicts a flowchart of a process used by the control system todetect theft using motion sensor output.

FIGS. 14C-14K depict schematics of the circuitry for implementing thetheft deterrence and detection system.

FIG. 15 depicts a flowchart of a partially automated process forcalibrating the rotary laser level system of FIG. 1.

FIG. 16 depicts a circuit diagram of the light detection system of thereceiver unit.

FIG. 17 depicts a schematic illustration of the rotational lightposition sensor.

FIG. 18 depicts a block diagram of the rotational light position sensor.

FIG. 19 is a schematic of the circuitry for implementing the rotationallight position sensor.

FIGS. 20-26 are schematics of additional circuitry for implementing therotational light position sensor.

DESCRIPTION

For the purposes of promoting an understanding of the principles of thedisclosure, reference will now be made to the embodiments illustrated inthe drawings and described in the following written specification. It isunderstood that no limitation to the scope of the disclosure is therebyintended. It is further understood that the present disclosure includesany alterations and modifications to the illustrated embodiments andincludes further applications of the principles of the disclosure aswould normally occur to a person of ordinary skill in the art to whichthis disclosure pertains.

The present disclosure is directed to a rotary laser level system 10that has a plurality of new and useful features, such as receiverdocking, theft prevention and detection, calibration reminders,partially automated calibration, and flatter bandwidths, which aredescribed in more detail below. Referring to FIGS. 1-3, the rotary laserlevel system 10 includes a base unit 12 and a receiver unit 14. The baseunit 12 comprises a housing 16 formed of a suitable hard, durablematerial, such as molded plastic. In the embodiment of FIGS. 1-4, thehousing 16 includes a front side portion 18, a rear side portion 20, aleft side portion 22, a right side portion 24, a top portion 26, and abottom portion 28 that collectively surround and define an interiorenclosure space. The housing 16 has a generally cubic shape although anysuitable shape may be used.

Referring to FIGS. 4 and 5, the bottom portion 28 of the housing 16 isconfigured to be placed against a surface, such as a floor or ground.The bottom portion 28 may include mounting features, such as mountingopenings 30, that enable the base unit 12 to be mounted to a tripod 32as depicted in FIG. 5, or to a wall bracket (not shown), or other typeof support structure. When the housing 16 is positioned with the bottomportion facing downwardly, the base unit 12 is in a horizontal position(defined by the orientation of the laser assembly). The housing 16 mayalso be configured for operation in a vertical position by positioningthe housing 16 with one of the sides facing downwardly. For example, inone embodiment, the rear portion 20 of the housing may be configured tobe placed on the floor or on the ground so the base unit 12 can beoperated in a vertical position.

Referring to FIGS. 3A and 3B, the top portion 26 of the housing 16defines an opening through which the rotating head portion 34 of a laserassembly extends. A transparent cap 36 is positioned over the headportion 34, and a protective cage 38 is mounted to the top portion overthe cap 36. Transparent windows are provided in the cap 36 to enable thelaser beams 40, 42 from the laser assembly to emanate out of the housing12. The protective cage 38 may be removably attached to the housing 12to provide access to the head portion 34 of the rotary laser so thelaser beam can be manipulated by an operator, e.g., to manually positionthe laser beam on a known point or work area.

The front portion 18 of base unit 12 includes a docking position 44 forremovably attaching the receiver unit 14 to the base unit 12. Asdepicted in FIG. 2, the docking position 44 includes support wallsand/or surfaces 46 that surround the docking position 44. Dockingfeatures (not visible) are provided in the docking position 44 forremovably retaining the receiver unit 14. The docking features may haveany suitable configuration that enables the receiver unit 14 to beoperably and removably retained on the base unit 12. Complementarydocking features are provided on the receiver unit 14. In oneembodiment, the docking features on the base unit 12 and the receiverunit 14 comprise rail and groove guide structures that are configured tocooperate to removably retain the receiver unit 14 in the dockingposition 44 on the base unit 12.

The base unit 12 includes two carrying handles 48 that project forwardlyfrom the housing 12 near each side of the front portion 18. Eachcarrying handle has a generally U-shaped configuration with an upperattachment portion extending from an upper portion of the housing and alower attachment portion extending from a lower portion of the housing.Ergonomic grip portions extend between the upper and lower attachmentportions to facilitate carrying the base unit 12. The carrying handlesalso serve to protect the docking position 44 on the front portion 18,and the receiver unit 14 if docked to the base unit 12, from impacts andfalls.

Referring to the block diagram of FIG. 6, the internal components of thebase unit 12 include a rotary laser assembly 50, a power system 52, acommunication system 54, a control system 56, and various sensors andindicators 58 (explained in more detail below). In one embodiment, thecontrol system 56, power system, and sensors 58 are implemented on thesame printed circuit board PCB A.

The rotary laser assembly 50 is operably mounted within the housing 12and includes a self-leveling support (not shown) and a laser module (notshown). In one embodiment, the self-leveling support structure comprisesa pendulum arrangement that is movably mounted within the housing. Thependulum arrangement is configured to automatically assume apredetermined orientation based on the inclination of the housing toprovide a reference position for the control system. For example, thependulum arrangement may be configured to use gravity and/or to use aleveling device, such as a servo-motor, to automatically level thependulum arrangement relative to the orientation of the housing.Self-leveling occurs automatically each time the housing is repositionedso long as the housing is stably supported and not inclined more than apredefined amount, e.g., 8%, relative to horizontal.

The laser module is incorporated into the rotating head portion 34 thatis rotatably mounted to the support structure. The laser module isconfigured to generate a plumb laser beam 40 and a rotary laser beam 42.The plumb laser beam 40 is emitted by the laser module verticallythrough the top of the protective cage 38 as depicted in FIG. 3. Therotary laser beam 42 is emitted by the laser module horizontally, e.g.,at 90° relative to the plumb beam 40. The laser beams 40, 42 may begenerated by the laser module in any suitable manner. For example, thelaser module may include one or more laser generators, such as a laserdiode or an array of laser diodes. The laser module may include any of avariety of laser control structures, such as lens, beam splitters,reflectors, collimators, and the like, so that the laser beams aregenerated with desired properties.

The head portion 34 is configured to rotate with respect to the supportstructure about a vertical axis. A drive system (not shown), such as amotor, is attached to the head portion 34 that is configured to causethe head assembly to rotate at one or more predetermined rotationalspeeds about the vertical axis. The drive system is also configured tocause the head portion and the laser module to rotate to a desiredangular position with respect to the axis and to oscillate within adesired angular range about the axis. The drive system may be configuredto allow manual positioning of the laser assembly which allows therotary laser beam to be pointed to a particular point or work surface bythe operator. In one embodiment, the laser assembly includes a lockingmechanism that is configured to hold the laser assembly in place whenthe base unit is turned off or put in a standby mode.

Referring to FIG. 7, the power system 52 for the base unit 12 isconfigured to run on battery power 60. Batteries for the base unit 12may have a nominal voltage, e.g., between 4 V and 50 V and may includecells having a chemistry of, for example, NiCd, NiMH, Li-ion, etc. Abattery tray or battery access panel (not shown) is provided in one ofthe surfaces of the housing 12 to enable batteries to be installed andremoved from the base unit 12. In one embodiment, the base unit 12 isconfigured to utilize 12V batteries. The base unit 12 may includeelectrical connections 62 for connecting the base unit 12 to an externalpower sources, such as an AC outlet, via a power cord. As depicted inFIG. 7, the power system 52 for the base unit 12 includes an internal,rechargeable battery 64 for powering the systems of the base unit 12.The internal battery 64 may comprise a Li-ion battery. The base unit 12is equipped with an internal battery charger 66 for charging therechargeable battery 64. The internal battery charger is configured toutilize power from the 12V battery 60 or from the external power sourcevia connection 62 to charge the internal Li-ion battery 64.

Referring again to FIG. 6, the control system 56 includes a controller68 and electronic storage, or memory 70. The controller 68 comprises aprocessing device, such as a central processing unit (CPU), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) device, or a microcontroller. The controller 68 isconfigured to execute programmed instructions that are stored in theelectronic storage 70 for controlling and operating the laser assembly.A real-time clock 57 for the control system 56 is implemented on a chipand has a separate battery, such as a Li-ion battery.

The controller 68 is configured to communicate with the receiver unit 14via the communication system 54. In one embodiment, the communicationsystem 54 comprises a radio frequency (RF) remote control system havinga RF transceiver for transmitting and receiving RF signals. The controlsystem 56 is configured to receive control signals from the receiverunit 14 via the communication system 54 and to execute commandsindicated by the control signals. The control signals from the receiver14 may be used to control the operating mode, aperture angle (for linemode), point angle (for point mode), power (ON/OFF), rotation speed, andthe like of the laser assembly. The operating modes include, forexample, a rotation mode (FIG. 8), a line mode (FIG. 9), and a pointmode (FIG. 10). In rotation mode, the rotary laser beam is moved at aconstant rotation speed around the axis of rotation and generates acontinuous laser marking on a target surface. In line mode, the rotarylaser beam is oscillated back and forth within a limited aperture angleto generate a line-shaped laser mark on a target surface. In point mode,the rotary laser beam is held stationary at a predetermined angularposition to generate a point-shaped laser mark on a target surface. Thecontrol system 56 may also be configured to transmit battery statusinformation and leveling status information to the receiver unit 14periodically or in response to requests received from the receiver unit14.

Referring to FIGS. 11A-11C, the receiver unit 14 for the rotary laserlevel comprises a small, portable housing 16 that is configured to bereceived and retained in the docking position 44 of the base unit 12.The housing 16 includes control elements 72, a speaker 74, one or moredisplay screens 76, and various gages and markings 78. The housing 16also includes docking features (not shown), such as rail and groovedocking guides, that enable the housing 16 to be removably retained inthe docking position 44. The receiver unit 14 also includes one or moremagnets (not shown) built into the housing 16 that are configured toenable the receiver unit 14 to be magnetically attached to metalsurfaces, such as suspended ceiling installations.

Referring to FIG. 12, the receiver unit 14 includes a control system 80,a rotational laser detection system 82, an audio indicator 83, a powersystem 84, an radio frequency (RF) transceiver 85 and a communicationsystem 86 that are supported by the housing 16. As depicted in FIG. 13,the power system 84 is configured to be powered by batteries 88 that areremovably received in a battery bay (not shown) provided in the housing16. Any suitable type and size of batteries may be used. The receiverunit 14 also includes an internal rechargeable battery 90, such as aLi-ion battery. The receiver unit 14 is equipped with an internalbattery charger 92 for charging the rechargeable battery. The internalbattery charger 92 is configured to utilize power from the removablebatteries 88 to charge the internal Li-ion battery. An AC adapterconnection 94 may also be provided for charging the internal battery 90.

Referring again to FIG. 12, the control system 80 for the receiver unit14 includes a controller 96 and electronic storage 98. The controller 96comprises a processing device, such as a central processing unit (CPU),an application specific integrated circuit (ASIC), a field programmablegate array (FPGA) device, or a microcontroller. The controller 96 isconfigured to execute programmed instructions that are stored in theelectronic storage 98 for controlling and the receiver unit 14 and thebase unit 12. The controller 96 is configured to send and receivecontrol signals to the base unit 12 via the communication system 86. Inone embodiment, the communication system 86 comprises a remote controlsystem configured to generate control signals for the base unit that aretransmitted via the RF transceiver 85.

The rotation laser detection system 82 includes light sensors (notshown) that are configured to receive and detect the laser beams 40, 42emitted by the base unit 12. The light sensors may comprise any suitabletype of light sensor, such as charge coupled devices (CCDs),photodiodes, and the like, that are capable of detecting the laser beamsemitted by the laser assembly of the base unit 12. The audio indicator83 may be activated in response to the detection of the laser beams. Thecontrol system 80 may also be configured to determine variousinformation in response to detecting a laser beam, such as beam centers,horizontal reference positions, vertical reference positions, anddistances from the base unit 12.

The control system 80 is operably coupled to receive input from thecontrol elements 72 on the housing. The control elements 72 may comprisepushbuttons, knobs, slides, and other types of switches that areconfigured to allow an operator to control the base unit 12 includingthe selection of the operating parameters of the laser assembly. Forexample, the control elements 72 may include control elements forcontrolling power to the receiver unit 14 and base unit 12 and forselecting the operating mode, scan angle, and rotation speed of thelaser assembly.

The control system 80 is configured to cause the display screen 76 todisplay status indicators, measurements, and other data regarding theoperation of the rotary laser level assembly. For example, the controlsystem may be configured to cause the display to indicate the currentoperating mode, rotation speed, scan angle, distance and positionmeasurements, battery status, and the like. The display screen 76 maycomprise any suitable type of display, such as a liquid crystal display(LCD). In one embodiment, the receiver unit 14 includes a display screen76 on both sides of the receiver 14 to allow easy viewing of statusindicators, measurements, and other data.

Docking

As discussed above, the receiver unit 14 is configured to be docked tothe docking position of the base unit 12. Complementary docking featureson the receiver unit 14 and the base unit 12 cooperate to enable thereceiver unit 14 to be removably retained on the base unit 12. Thereceiver unit 14 can be docked to the base unit 12 when not in use tofacilitate transportation and storage of the rotary laser levelassembly. As can be seen in FIG. 1, the carrying handles 48 projectforwardly beyond the receiver unit 14 which allows the carrying handles48 to shield and protect the receiver unit 14 from impacts and fallswhen docked to the base unit 12.

The base unit 12 is configured to detect when the receiver unit 14 isdocked to the docking position of the base unit 12. In one embodiment,the base unit 12 is equipped with a magnetic reed switch 102 (FIG. 6)that is implemented on docking board PCB 55 (separate PCB from thecontrol system PCB A) which is mounted to the inner wall of the basehousing for detecting the presence of the magnets of the receiver unit14 in the docking position. Alternatively, the base unit 12 may includeother types of sensors, such as magnet sensors, light sensors, proximitysensors, capacitive sensors, and the like, that are configured to detectvarious conditions indicative of the receiver unit 14 being docked tothe base unit 12.

Referring to FIGS. 7 and 13, the power system 52 for the base unit 12may include electrical connections 104, e.g., charge terminals, locatedin the docking position 44 for connecting to complementary electricalconnections 106 on the receiver unit 14 so that, when the receiver unit14 is docked to the base unit 12, the receiver unit 14 can receive powerfrom the power source 60 of the base unit 12. In this case, the internalbattery charger 92 for the receiver unit 14 is configured to utilizepower via the base unit 12 to charge the internal Li-ion battery 90. Inturn, the base unit is powered by the adaptor. This allows forsimultaneous charging of the base unit 12 and receiver unit 14 when thereceiver unit 14 is docked. The control system 56 of the base unit 12may be configured to control power to the electrical connection 52 inorder to remove power from the electrical connection 52 when the docksensors 102 indicate the receiver unit 14 is not docked. The electricalconnections 104 of the base unit 12 may be sealed to prevent wateringress and to achieve a desired ingress protection (IP) rating. In oneembodiment, the charge terminals of the base unit 12 are sealed byo-ring seals. The o-ring seals are positioned against the printedcircuit board assembly (PCB A) onto which the charge terminals aresoldered.

The receiver unit 14 and base unit 12 are configured to be pairedtogether to enable two-way communication and control of the base unit 12by the receiver unit 14. In one embodiment, device pairing is performedwhen docking occurs. For example, when the dock sensor 102 indicatesthat a receiver unit 14 is docked to the base unit 12, the controlsystem 80 of the base unit 12 transmits a unique identifier, such as anaddress, ID number, serial number, and the like, (previously assigned tothe base unit 12) to the receiver unit 14. The receiver unit 14 can thenuse this unique identifier to communicate with the base unit 12.Multiple receiving units 14 may be paired with the base unit in thismanner so that multiple receiver units can be used to operate the samebase unit 12. Pairing the base unit 12 with one or more receiver unitsenables more than one base unit 12 to be operated in an area without thereceiver units for one base unit 12 interfering with the operation ofother base units. In an alternative embodiment, the base unit 12 may beconfigured to be paired with a single receiving unit 14 or a set numberof receiving units 14 at a time. An option to pair the base unit 12 withmultiple receiving units 14 or a single receiving unit 14 may beprovided as a user selectable item in the control system.

Theft Prevention and Detection Features

The rotary laser level assembly includes theft prevention and detectionfeatures in order to reduce the possibility of theft of the base unit12. A first theft prevention feature is provided by the fact that noswitches or displays are incorporated into the base unit 12. All of thecontrols and displays for operating the rotary laser level assembly areincorporated into the receiver unit 14. When the receiver unit 14 is notdocked, it is obvious from the lack of a user interface and the emptydocking position that the product is incomplete. This is a passive theftprevention feature.

The base unit 12 also includes a second theft prevention feature foractive theft prevention. The second theft prevention feature comprises atheft detection and deterrence system incorporated into the base unit 12that can be activated and deactivated by the receiver unit 14. Referringto FIG. 14A, the theft detection and deterrence system includes an alarmactive indicator 108, a theft detector 110, a RF transceiver 113, andtheft indicators 110. The alarm active indicator 108 comprises a visualindicator, such as a flashing LED light, provided on the base unit 12.The alarm active indicator 108 is actuated when the base unit 12 ispowered on, or in a standby mode, to indicate that an alarm is active(which may also indicate that the base unit 12 is operational so anoperator may be nearby) to serve as a theft deterrent.

The theft detector 110 comprises a motion sensor, such as a MEMSaccelerometer, incorporated into the base unit 12 to detect when thebase unit 12 is being moved. The motion sensor is configured to outputX, Y, and Z acceleration values for indicating movement inthree-dimensions. Using movement for theft detection is based on thefact that the base unit 12 must be stationary when operational. Whenmovement of the base unit 12 is detected, one or more theft indicators112 may be actuated. In one embodiment, the control system 56 may beconfigured to activate the theft indicators 112 only after movement of apredefined duration has been detected so that alarms are not activatedin response to an innocent situation, such as the base unit 12 beingjostled by wind or someone or something inadvertently bumping into thebase unit 12 causing the base unit 12 to move slightly.

The theft indicators 112 may comprise audio and/or visual indicatorsthat are used to draw attention to the area and alert nearby personnelthat a theft is occurring. For example, in one embodiment, the base unit12 includes a speaker system for generating an alarm sound, such as loudbuzzing, sirens, beeps, or combinations of different sounds. One or morevisual indicators, such as LEDs, may be illuminated and/or flashed toindicate theft. In one embodiment, the alarm active indicator 108, whichotherwise generates a constant, cool and/or slowly blinking light may bemade brighter and/or flashed more rapidly to indicate theft. Thereceiver unit 14 can be used to deactivate the theft indicators 112 bycommunicating a deactivation signal from the RF transceiver 85 of thereceiver to the RF transceiver 113 of the theft deterrence system.

Referring to FIG. 14B, a flowchart of a process of monitoring the outputof the motion sensor 110 to determine whether or not an alarm should begenerated. At block 1400, the X, Y, and Z acceleration values fromoutput of the motion sensor 110 are acquired. The control system 56 isconfigured to maintain a short term running average of the X, Y, and Zvalues, e.g., a 16pt running average (block 1402). The control system 56is also configured to maintain a long term running average of the X, Y,and Z values, e.g., a 64pt running average (block 1404). The controlsystem 56 is configured to calculate a MOVEMENT value which correspondsto the long term average minus the short term average (block 1406).

At block 1408, the MOVEMENT value is compared to a threshold value nthat has been determined to be indicative of movement of the base unit.In the embodiment of FIG. 14B, the threshold value n for movement is 5.The control system is configured to maintain a running count, referredto as THEFT_COUNT in FIG. 14B, that is incremented each cycle thatmovement is detected (i.e., MOVEMENT>n) and decremented each cycle thatmovement is not detected (i.e., MOVEMENT<n). According to the flowchart,if MOVEMENT<n, movement is not detected and control proceeds to block1410. At block 1410, it is determined whether or not THEFT_COUNT isequal to 0. If THEFT_COUNT is not equal to 0, then THEFT_COUNT isdecremented at block 1412. If THEFT_COUNT is equal to 0, then block 1412is bypassed so that THEFT_COUNT is not decremented. Therefore,THEFT_COUNT should never be less than 0.

At block 1414, THEFT_COUNT is compared to a lower limit threshold valuefor duration of movement of the base unit that may indicate theft. Inthe embodiment of FIG. 14B, the lower limit threshold value is selectedto be 500. If THEFT_COUNT is greater than 500, then theft may beindicated and an alarm is generated at block 1416. If THEFT_COUNT isless than the lower limit threshold (n=500), then block 1416 isbypassed. At block 1418, there is a delay (e.g., 10 mS) before returningto block 400 to perform another cycle.

At block 1408, if MOVEMENT is greater than n, control proceeds to block1420 and THEFT_COUNT is compared to an upper limit threshold value(e.g., n=750). If THEFT_COUNT is less than 750, THEFT_COUNT isincremented at block 1422. If THEFT_COUNT is greater than or equal to750, control bypasses block 1422 so that THEFT_COUNT is not incremented.In either case, control proceeds to block 1414 where THEFT_COUNT iscompared to the lower limit threshold value (e.g., n=500). Theschematics for the circuitry of the theft deterrence and detectionsystem are depicted in FIGS. 14C-14K.

Calibration Reminders

The base unit 12 may require periodic servicing to calibrate the laserassembly so as to maintain the precise horizontal and verticalorientations of the rotary and plumb laser beams. Scheduling theservicing or reminding the operator to check the calibration istypically the responsibility of the owner/operator of the tool. Therotary laser level assembly includes an integrated electroniccalibration reminder system that is configured to remind the operator ofthe need to periodically check the calibration of the base unit 12 andto have the base unit 12 serviced at regular intervals.

The reminder system is configured to generate service reminders andcalibration reminders. The service reminders are timed reminders forindicating when servicing needs to be performed. There are two types oftimed service reminders, one type of service reminder is based onpredefined intervals and another type of service reminder based on hoursof operation. The predefined service intervals and hours of operationlimits may be based on factory specifications and programmed into theelectronic storage 70 of the control system 56 of the base unit 12. Thecontrol system 56 of the base unit 12 is configured to monitor elapsedtime between servicing as well as hours of operation, i.e., run time,and to generate a service reminders to indicate when a predefinedservice interval or hours of operation limit has expired.

Calibration reminders are generated in response to operating conditionsand events that can alter the calibration of the base unit 12. Forexample, the base unit 12 is configured to be operated withinpredefined, factory-specified temperature and humidity limits.Temperature and humidity limits may be specified for storage as well asoperation of the base unit 12 may be specified. Operating or storing thebase unit 12 in temperature and humidity conditions outside of theselimits can adversely impact the calibration of the system. Calibrationcan also be altered by shocks to the base unit 12 that may result fromdrops, falls, and impacts.

Referring to FIG. 6, the base unit 12 includes sensors 114, 116, 118 fordetecting environmental conditions as well as shocks and impacts to thebase unit 12 that can alter calibration so that calibration reminderscan be generated to indicate that the calibration of the base unit 12should be checked. The sensors include temperature and humidity sensors114, 116 for detecting the temperature and humidity of the environmentin and around the base unit 12. When the base unit 12 is powered off,the control system 56 for the base unit 12 is configured to wake theelectronics of the system at predefined intervals in order to activatethe temperature and humidity sensor to measure the temperature andhumidity.

The control system 56 is configured to compare the detected temperatureand humidity to the storage limits for temperature and humidity. Ifeither of these values exceeds the storage specifications for the baseunit 12, the incident is logged and a calibration reminder is given nexttime the unit is powered on. When the base unit 12 is powered on, or instandby mode, the control system is configured to generate a calibrationreminder immediately when the sensors 114, 116 indicates that theoperating specifications for temperature and/or humidity have beenexceeded.

The shock sensors 118 for the base unit 12 comprise three piezo sensorsarranged at right angles with respect to each other to detect shock inall three spacial planes. The sensitivity of the piezo sensors andassociated electronics are set so as to trigger when the unitexperiences a shock large enough to possibly alter the calibration.Detection of shocks is possible when the base unit 12 is powered on, instandby, or powered off. If the base unit 12 is powered on, or instandby, the control system 56 is configured to generate a calibrationreminder immediately when the shock sensors are triggered. When thedevice is powered off, the piezo sensors generate a voltage that wakesthe control system 56 to log the shock event. A calibration reminder maythen be issued the next time the base unit 12 is powered on.

Because the base unit 12 does not have a display, any service andcalibration reminders are communicated to the receiver unit 14. Thereceiver unit 14 includes one or more reminder indicators for indicatingthe reminders. Reminder indicators may comprise icons that can bedisplayed on the display screen of the receiver unit 14. Multipleindicators or icons may be used to indicate the type of reminder andwhat triggered the reminder. For example, a main reminder indicator maybe displayed to indicate that service is required or calibration shouldbe checked. Additional indicators may be displayed to indicate whetherthe reminders are based on shock, temperature, humidity or time. Inaddition to providing the user with service and calibration reminders,the control system of the base unit 12 logs all the service andcalibration reminder events in memory 70. The log can be accessed duringservicing and repair of the base unit 12 to help in fault diagnosis andfuture product development.

Partially Automated Calibration

As mentioned above, calibration reminders may be generated in responseto operating conditions or shocks to the base unit 12 being detectedthat can alter the calibration of the base unit 12. The presentdisclosure proposes a method for partially automating the calibrationprocess of the level position of the base unit 12. The method leveragesthe two-way RF communication built into the base unit 12 and receiverunit using the receiver unit 14 to detect the position of the laser beamand allowing the base unit to automatically adjust level position to thereceiver unit 14.

Referring to FIG. 15, the method begins with powering on the base unit12 and initiating a calibration routine through the receiver unit 14(block 200). When the base unit 12 is powered up, the laser assembly ofthe base unit 12 automatically levels itself (block 204). Once the laserassembly has initially leveled, the receiver unit 14 is used to locatethe center of the laser beam 42. The receiver unit 14 is then locked inthis position (block 208). For example, the receiver unit 14 can beplaced on a support surface or magnetically attached to a metal wall.

The operator then rotates the base unit 12 180° about the axis ofrotation and waits for the base unit 12 to self-level (block 210). Thebase unit 12 will then center the laser beam 42 on the receiver unit 14.The control system 56 of the base unit 12 reads the internal levelposition of the laser assembly and calculates a new level position(block 212). The control system then compares the new level position tothe previous level position (block 208). If the control systemdetermines that the new level position is within a predefined limit fromthe previous level position, then the control system 56 can signal thereceiver unit 14 that the calibration procedure is complete (block 214).If the new level position is outside of the predefined limit, thecontrol system stores the current level position as the initial levelposition and performs the calibration process again.

Laser Position Detection

In one embodiment, the rotational laser system 82 of the receiver unit14 has a configurable bandwidth for controlling the distance over whichthe system 82 is capable of detecting the beam center. With mostpreviously known laser receivers the bandwidth varies with distance. Forexample, higher bandwidths typically allow the beam center to bedetected over larger distances but the accuracy of the measurement isdecreased while lower bandwidths typically allow greater accuracy butdecrease the distance over which the beam center can be detected. Theabsolute bandwidth values are specified at a specific distance as thelaser beam diverges with distance. The present disclosure proposes asensor system design capable of decreasing the variation of thebandwidth with distance so that the light detection system has a flatteroverall detection bandwidth. This will enable greater accuracy at longerdistances than previously known detection systems for receiver units.

In accordance with one embodiment, a method of detecting a laser beamemitted by a rotary laser tool includes receiving light via an opticalwindow of the receiver unit, and directing the light received via theoptical window onto a first light sensor array and a second light sensorarray. At least one signal is output from the first light sensor arrayindicating a characteristic of the light incident upon the first lightsensor array. At least one signal is output from the second light sensorarray indicating a characteristic of the light incident upon the secondlight sensor array. The at least one signal from the first light sensorarray and the at least one signal from the second light sensor array areprocessed with respect to each other to produce a measurement signal. Adetermination is then made whether the received light is a laser beamemitted by the laser tool based on the measurement signal.

In another embodiment, a laser receiving unit configured to laserdetection includes a portable housing having an optical windowconfigured to allow light to pass into the housing. A laser light sensorassembly is mounted within the housing that includes a first lightsensor array and a second light sensor array. At least one linearmultiple stage amplifier is coupled to receive an output of the firstlight sensor array and to produce a plurality of amplified first signalsfrom the output of the first light sensor with substantially lineargain. At least one linear multiple stage amplifier is coupled to receivean output of the second light sensor array and to produce a plurality ofamplified second signals from the output of the second light sensor withsubstantially linear gain. A control system is coupled to receive eachof the amplified first signals and each of the amplified second signalsand configured to process the amplified signals to determine whetherlight incident upon the first light sensor array and the second lightsensor array is from a laser beam emitted by the laser tool.

Referring to FIG. 16, a rotational laser detection system 130 includestwo light sensors 132, 134 which may be built from discrete components.On the optical side, the detection system 130 comprises an optic filterwindow 136, a micro lens 138, and photodiode arrays 140, 142 mounted ona printed circuit board 144. The optical filter window 136 is configuredto block unwanted light. The micro lens 138 is configured to spray thelight over the adjacent photodiodes 140, 142 of the detectors 132, 134.The photodiode arrays 140, 142 are configured to convert the receivedlight into a proportional current. Based the sensor information fromeach sensor array, overall characteristics of the light incident on thesensor arrays may be determined. Because the light sensor is split intotwo parts, detection of the center point of the beam is more accurate.This also provides a technique for strobe detection and rejection.

FIG. 17 depicts one embodiment of a circuit for processing output of thephotodiode arrays 140, 142 for laser detection. In the embodiment ofFIG. 17, the output of the photodiode array 140 is directed to a firstlinear multiple stage amplifier 124, and the output of the output of thephotodiode array 142 is directed to a second linear multiple stageamplifier 126. A multiple stage amplifier provides better linearity foramplifying the received signal. In the embodiment of FIG. 17, two fourstage amplifiers are utilized although more or fewer stages could beused.

The stages of the amplifiers 124, 126 are configured to provide asubstantially linear gain. The amplified signal from each stage of theamplifiers 124, 126 is received by the control system 80, e.g.,implemented on the circuit board 144. The control system 80 of thereceiver unit 14 is configured to select the amplified signals from theamplifier stage(s) having the best signal, e.g., the highestsignal-to-noise ratio, for detecting the laser beam. The amplitude ofthe selected signal, i.e., the gain, is then used to scale thebandwidth. In this manner, the variation of bandwidth with distance canbe reduced so a “flatter” detection bandwidth is provided.

As an alternative to the rotational laser detection system of FIG. 17,the receiver unit may be provided with a rotation laser detection systemas depicted in FIG. 18. The rotational laser detector of FIG. 18 iscapable of an accuracy within a range of +−0.5 mm over the surface ofthe laser detector sensor. The rotational laser detector of FIG. 18includes electronics for actively compensating for sunlight andflorescent light falling on the sensors. This electronics also hasadditional light intensity output signals which can be fed to themicro-controller. By monitoring the sunlight intensity over the surfaceof the sensor, predictions on its linearity can be made ensuring noerroneous measurements are generated.

Referring to FIG. 18, the two laser position sensor detectors 132, 134of the laser detection system 130 are built from discrete components. Onthe optical side the detection system 130 comprises an optic filterwindow 136, a micro lens 138, and photodiode arrays 140, 142 mounted ona printed circuit board 144. The optical filter window 136 is configuredto block unwanted light. The micro lens 138 is configured to spray thelight over the adjacent photodiodes 140, 142 of the detectors 132, 134.The photodiode arrays 140, 142 are configured to convert the receivedlight into a proportional current.

Referring to FIG. 19 in addition to FIG. 18, the currents produced bythe photodiodes (e.g., D1-D11) in the photodiode array 140 are steeredby resistors (e.g, R1-R10) to two transimpedance amplifiers 146, 148,i.e., top transimpedance amplifier (TTA) and middle top transimpedanceamplifier (MTTA). The currents produced by photodiodes (e.g., D12-D22)of photodiode array 142 are steered by resistors (e.g., R11-R20) to twotransimpedance amplifiers 150, 152, i.e., middle bottom transimpedanceamplifier (MBTA) and bottom transimpedance amplifier (BTA).

The distribution of photodiodes receiving incident light as well as theintensity of incident light on the photodiodes governs the proportion ofcurrent that will be steered to each amplifier. The difference betweenthe amplifier signal outputs will therefore be able to indicate acharacteristic of the light incident upon the sensor arrays, such as theportion of the sensor array receiving incident light and/or a positionor positions on the sensor receiving incident light.

A light compensator is associated with each transimpedance amplifier.For example, a top light compensator (TLI) 154 is associated with thetop transimpedance amplifier 146, a middle top compensator (MTLI) 156 isassociated with the middle top transimpedance amplifier 148, a middlebottom light compensator (MBLI) 158 is associated with the middle bottomtransimpedance amplifier 150, and a bottom light compensator (BLI) 160is associated with the bottom transimpedance amplifier 152.

The outputs of the sensor board 144 (FIG. 17) include the outputs of thefour transimpedance amplifiers 146, 148, 150, 152 and the outputs offour light compensators 154, 156, 158, 160 all of which are communicatedto the control system 80 of the receiver 14. The control system 80 isconfigured to compare the difference of the four outputs of thetransimpedance amplifiers 1, 3, 5 and 7 to determine the position of thelaser beam on the sensor. If the signal from all the amplifiers issimilar, the sensor has been hit by a strobe light. The four lightintensity outputs of the light compensators 154, 156, 158, 160 give anindication of the sunlight intensity and distribution over the entiresensor.

Additional electronics is required to interface the sensors output tothe analog to digital converters of the controller 96. Firstly, peakdetectors PD are used hold the peaks of the detected light pulses.Secondly, peak amplifiers PA are used to further amplify the sensorsignals for long range detection, and thirdly, peak interrupt generatorsINT are used to generate an interrupt to the controller every time apeak is detected. After an interrupt is received the controller 96 willmeasure the peaks using its integrated analog to digital converters. Theschematics for the additional circuitry of the laser sensor, which alsoincludes the micro-controller are depicted in FIGS. 20-26.

While the disclosure has been illustrated and described in detail in thedrawings and foregoing description, the same should be considered asillustrative and not restrictive in character. It is understood thatonly the preferred embodiments have been presented and that all changes,modifications and further applications that come within the spirit ofthe disclosure are desired to be protected.

What is claimed is:
 1. A method of detecting a laser beam emitted by alaser tool, the method comprising: receiving light via an optical windowof a receiver unit; directing the light received via the optical windowonto a first light sensor array and a second light sensor array, thefirst and the second light sensor arrays being arranged adjacent to eachother within the housing; outputting at least one signal from the firstlight sensor array indicating a characteristic of the light incidentupon the first light sensor array; outputting at least one signal fromthe second light sensor array indicating a characteristic of the lightincident upon the second light sensor array; processing the at least onesignal from the first light sensor array and the at least one signalfrom the second light sensor array with respect to each other to producea measurement signal; and determining whether the received light is alaser beam emitted by the laser tool based on the measurement signal. 2.The method of claim 1, further comprising: directing the at least onesignal from the first light sensor array to a first multiple linearstage peak amplifier, each respective amplifier stage of the firstmultiple linear stage amplifier outputting an amplified first signalwith a predetermined gain; directing the at least one signal from thesecond light sensor array to a second multiple linear stage peakamplifier, each respective amplifier stage of the second multiple linearstage amplifier outputting an amplified second signal with apredetermined gain; processing the amplified first signals and theamplified second signals with respect to each other to produce ameasurement signal for each amplifier stage of the first and the secondmultiple linear stage amplifiers; selecting the measurement signal fromthe amplifier stage having the highest signal-to-noise ratio; anddetermining whether the received light is a laser beam emitted by thelaser tool based on the selected measurement signal.
 3. The method ofclaim 2, further comprising: scaling the selected measurement signalbased on the amplifier stage of the selected measurement signal.
 4. Themethod of claim 2, wherein each of the first and the second multiplelinear stage peak amplifier has four stages.
 5. The method of claim 2,further comprising: peak detectors associated respectively with each ofthe amplifier stages of the first multiple linear stage peak amplifier,each of the peak detectors being configured to receive one of theamplified first signals or the amplified second signals and to output asignal indicating a peak level of the received signal.
 6. The method ofclaim 1, further comprising: amplifying a first signal received from afirst end of the first light sensor array at a first multiple stagelinear amplifier; amplifying a second signal received from a second endof the first light sensor array at a second multiple stage linearamplifier to produce a second amplified signal; amplifying a thirdsignal received from a first end of the second light sensor array at athird multiple stage linear amplifier to produce a third amplifiedsignal; amplifying a fourth signal received from a second end of thesecond light sensor array at a fourth multiple stage linear amplifier toproduce a fourth amplified signal; processing the first amplifiedsignal, the second amplified signal, the third amplified signal, and thefourth amplified signal with respect to each other to produce themeasurement signal; and determining whether the received light is alaser beam emitted by the laser tool based on the measurement signal. 7.The method of claim 6, further comprising: generating an amplifiedsignal at each stage of each of the first, second, third, and fourthmultiple stage linear amplifier; processing the amplified signalsproduced by each stage of the of the first, second, third, and fourthmultiple stage linear amplifiers with respect to each other to produce ameasurement signal for each stage of the first, second, third, andfourth multiple stage linear amplifiers; selecting the measurementsignal from the amplifier stage with the highest signal-to-noise ratio;and determining whether the received light is a laser beam emitted bythe laser tool based on the selected measurement signal.
 8. The methodof claim 7, wherein each of the, second, third, and fourth multiplestage linear amplifiers includes a transimpedance amplifier.
 9. Themethod of claim 8, wherein a light compensator is associated with eachof the transimpedance amplifiers, the light compensators beingconfigured to output signals indicating an intensity and/or distributionof sunlight on the on the first and the second light sensor arrays. 10.The method of claim 1, further comprising: filtering light such thatonly light of a predetermined wavelength or range of wavelengths ispermitted to pass through the optical window.
 11. The method of claim 1,further comprising: using a lens to spread light received via theoptical window so the light is incident upon both the first and thesecond sensor array.
 12. A laser receiving unit for a laser tool, thelaser receiving unit comprising: a portable housing; an optical windowon the portable housing configured to allow light to pass into thehousing; a laser light sensor assembly mounted within the housing andincluding: a first light sensor array; a second light sensor array; atleast one linear multiple stage amplifier coupled to receive an outputof the first light sensor array and to produce a plurality of amplifiedfirst signals from the output of the first light sensor, each of theamplified first signals having a different gain; at least one linearmultiple stage amplifier coupled to receive an output of the secondlight sensor array and to produce a plurality of amplified secondsignals from the output of the second light sensor, each of theamplified second signals having a different gain; and a control systemcoupled to receive each of the amplified first signals and each of theamplified second signals and configured to process the amplified firstsignals and the amplified second signals to determine whether lightincident upon the first light sensor array and the second light sensorarray is from a laser beam emitted by the laser tool.
 13. The receivingunit of claim 12, wherein the control system is configured to processthe amplified first signals and the amplified second signals to identifya stage of the first and the second linear multiple stage amplifiersthat produces amplified signals with the highest signal-to-noise ratioand to use the amplified signals from the identified stage for themeasurement signal.
 14. The receiving unit of claim 13, wherein thecontrol system is configured to scale a bandwidth of the measurementsignal based on the identified stage.
 15. The receiving unit of claim13, wherein the at least one multiple stage amplifier coupled to receivean output of the first light sensor array includes a first linearmultiple stage amplifier coupled to receive a first output from a firstend of the first light sensor array and a second linear multiple stageamplifier coupled to receive a second output from a second end of thefirst light sensor array, and wherein the at least one multiple stageamplifier coupled to receive an output of the second light sensor arrayincludes a third linear multiple stage amplifier coupled to receive afirst output from a first end of the second light sensor array and afourth linear multiple stage amplifier coupled to receive a secondoutput from a second end of the second light sensor array.
 16. Thereceiving unit of claim 15, wherein the first, second, third, and fourthlinear multiple stage amplifiers each include a transimpedanceamplifier.
 17. The receiving unit of claim 16, further comprising alight compensator associated with each of the transimpedance amplifiers,the light compensators being configured to output signals indicating anintensity and/or distribution of sunlight on the first and the secondlight sensor arrays.
 18. The receiving unit of claim 15, wherein theoptical window includes an optical filter configured to pass only lightof a predetermined wavelength or range of wavelengths.
 19. The receivingunit of claim 15, further comprising: a lens for spreading lightreceived via the optical window so the light is incident upon both thefirst and the second light sensor array.